Method of viewing optical fiber connection residing in polishing workholders and apparatus used therefor

ABSTRACT

An apparatus that enables a magnification system to view the surface of optical connectors without the need to remove the connectors from a polishing workholder. A connector is placed into a centering insert that is integral to a polishing workholder. The magnification system is fitted with an adapter that engages with the centering insert. This engagement locates the ferrule of the optical connector in the focal plane of the magnification system for viewing and inspection of surface quality.

FIELD OF THE INVENTION

[0001] The present invention generally relates to a method and to devices enabling the viewing and inspection of the surface quality of optical fiber connectors, and more particularly to an engagement apparatus that permits viewing and inspection while said connectors reside in a polishing workholder.

BACKGROUND OF THE INVENTION

[0002] Fiber optic cables are presently used as a transmission media for telecommunication, data communications, video, cable television, sensing systems, power and telemetry. In order to extend cable span lengths, link various fiber segments together, and access terminal equipment such as transmitters and receivers, fiber optic connectors are utilized. Fiber optic connections can be opened and reconnected multiple times providing flexibility for network routing, access and reconfiguration.

[0003] Fiber optic connectors are terminated on the end of an optical fiber. A typical connector consists of a cylindrical ferrule in which an optical fiber is centered and mounted. The connector is secured to the fiber and cable by either adhesive or mechanical gripping means.

[0004] The final step in the termination of a fiber optic connector is the polishing of the fiber end face. The terminated connector is placed into a polishing workholder. Typically, the workholder is a jig device shaped like a disk. When inserted into the workholder, a small portion of the connector ferrule extends beyond the bottom workholder surface. The workholder is precisely machined to hold the connector either perpendicular or at a predetermined angle in reference to a polishing platen.

[0005] Abrasive polishing films are placed on the platen. As the workholder repetitively moves the ferrule across the film, fiber surface material is removed. Several types of films, varying in the degree of abrasiveness, may be used in the process. The end desired result is a smooth, scratch and defect-free fiber surface finish. This procedure results in a low loss and high performing connector.

[0006] In order to insure a correct fiber finish, the connector end face needs to be inspected. A microscope usually accomplishes this task. Suitable microscopes include manual units with eyepieces for direct viewing and video devices for viewing the magnified connector image on a monitor.

[0007] Prior art demonstrates adapters on microscopes that permit stand-alone connectors to be individually inserted into the microscope. This necessitates the removal of the connector from the workholder before inspection and reinsertion after inspection if additional polishing is required. This excessive material handling is time consuming. Labor rates are a large contributor to overall connector termination costs. This is not acceptable in the very cost sensitive connector industry.

[0008] The excessive material handling of prior art is compound with the introduction of automated mass polishing units that have workholders capable of holding and polishing from 12 to 48 connectors simultaneously. Each one of these connectors needs to be removed from the workholder, one-by-one, for individual inspection.

[0009] A significant shortcoming of prior art is that the required excessive material handling increases the possibility of particle contamination and potential damage to the fiber surface.

[0010] The introduction of new connector types and performance specifications requires the development of advanced polishing techniques and procedures. This research involves intensive testing involving different polishing speeds, polishing pressure and abrasive films. Constant microscopic inspection is required during all stages of this development process. Prior art makes this tedious because of the need to remove and reinsert connectors into and out of workholder and microscope.

[0011] Many types of optical connector styles are offered in the marketplace. These styles differ in connector hardware and ferrule sizes. Prior art requires a microscope to have different adapters for each type of connector to be inspected. This necessitates the continual changing of adapters in order for the microscope to accept connectors for viewing.

SUMMARY OF THE INVENTION

[0012] Therefore, it is the object of the invention to provide a convenient means for viewing the end faces of optical fiber connectors without removing them from a polishing workholder.

[0013] An advantage of the present invention is to provide an engagement system between a polishing workholder and a viewing microscope. This engagement will align the connector end face with the focal plane of the microscope.

[0014] Still another advantage of the present invention is that the said engagement does not rely upon the connector type or ferrule size and shape. The engagement mechanism is integral to the workholder and microscope interface.

[0015] A further advantage of the present invention is that it vastly decreases material handling since it does not require a connector to be removed from the polishing workholder in order to inspect its end face with a microscope instrument.

[0016] An additional advantage of the present invention is that the resulting decrease in material handling significantly reduces possible connector contamination and damage.

[0017] It is still another advantage that the present invention does not require a multitude of individual connector adapters to be interchanged on a microscope in order to view varying styles of connector types and ferrule sizes.

[0018] The present invention also has the advantage of minimizing the amount of microscope focus adjustment since the engagement mechanism automatically aligns the connector end face with the microscope focal plane.

[0019] An advantage of the present invention is that the engagement mechanism does not make physical contact with the optic connector. The only contact is between the microscope and the workholder. This minimizes potential connector damage and contamination.

[0020] Other advantages of the invention will become apparent upon reading the following detailed description and appended claims, and upon reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] For a more complete understanding of this invention reference should now be had to the embodiments illustrated in greater detail in the accompanying drawings and described below by way of examples of the invention.

[0022]FIG. 1 is an isometric view of the preferred embodiment's centering means.

[0023]FIG. 2 is a cross sectional view of centering means with an optical connector inserted.

[0024]FIG. 3A is an isometric view of centering means mounted within a polishing workholder.

[0025]FIG. 3B is a cross sectional view of centering means mounted within a polishing workholder.

[0026]FIG. 4A is an isometric view of the embodiment's adapter means.

[0027]FIG. 4B is a cross sectional view the adapter means.

[0028]FIG. 5 is a cross sectional view of the adapter means engaged with an optical magnification means.

[0029]FIG. 6 is a cross sectional view of the embodiment illustrating the engagement between the centering means and adapter means.

[0030]FIG. 7 is an isometric view of another embodiment of the present invention illustrating a centering means mounting in a polishing workholder.

[0031]FIG. 8 is cross sectional view of the embodiment of FIG. 7 illustrating the engagement between the adapter means and the optical magnification means.

[0032]FIG. 9 is a cross sectional view of the embodiment of FIG. 7 illustrating the engagement between the centering means and adapter means.

[0033]FIG. 10 is an isometric view of another embodiment of the present invention illustrating the locating means of the polishing workholder.

[0034]FIG. 11 is a cross sectional view of the embodiment of FIG. 10 illustrating the adapter means engaged with an optical magnification means.

[0035]FIG. 12 is cross sectional view of the embodiment of FIG. 10 illustrating the engagement between the adapter means and the locating means.

[0036] While the invention will be described in connection with a preferred embodiment, it will be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0037] Referring to FIG. 1, apparatus 1 is provided with a centering means 20. Centering means 20 is tubular in shape. Suitable tubular cross-sections include circular, elliptical, square and rectangular. Circular is preferred. Suitable materials for centering means 20 include stainless steal, aluminum and brass. Stainless steel is preferred. Center means 20 is provided with a closed end 22 and an open end 24. Closed end 22 is provided with a chamfer 26. Closed end 22 is also provided with a through hole 28. Through hole 28 is aligned with the center axis of centering means 20.

[0038] Referring next to FIG. 2, through hole 28 has a diameter large enough to accept a ferrule 30 of an optical connector 32. The inner diameter of center means 20 is large enough to accept the insertion of connector 32. When connector 32 is inserted into centering means 20, ferrule 30 protrudes beyond the surface of closed end 22.

[0039] Referring now to FIG. 3A, a polishing workholder 34 is illustrated. Suitable polishing workholders include those manufactured by Krell Technologies, Englishtown, N.J., having part numbers SM3-10 and SP3-10. Polishing workholder 34 is provided with a plurality of through holes 36. Centering means 20 are inserted and mounted in through holes 36. Mounting means include press-fitting and epoxy. As illustrated in FIG. 3B, centering means 20 is positioned so that the bottom of chamfer 26 is above the surface of polishing workholder 34.

[0040] An adapter means 38 is illustrated in FIG. 4A. Adapter means 38 has the same tubular shape as centering means 20. Suitable materials for adapter means 38 are stainless steel, aluminum, brass and polymer plastics. Stainless steel is preferred. The inner diameter of adapter means 38 is large enough to accept the outer diameter of centering means 20. A slip fitting between adapter means 38 and centering means 20 is preferred. One end of adapter means 38 has internal threading as shown in FIG. 4B.

[0041] Referring to FIG. 5, an optical magnification means 42 is illustrated. Suitable optical magnification means include microscopes, fiberscopes, borescopes and video inspection systems. The SpecVision Video Inspection System manufactured by Krell Technologies, Inc., Englishtown, N.J., having a part number SV3 is preferred. Magnification means 42 is provided with an objective 44 attached at a base 46. Base 46 has an external threading 48 which permits engagement with the internal threading 40 of adapter means 38. Adapter means 38 is of sufficient length, that when attached to base 46 through the engagement of threading 40 and threading 48, the focal plane 50 of objective 44 lies within adapter means 38. When attached to base 46, the center axis of adapter means 38 coincides with the optical train axis 52 of magnification means 42.

[0042] The operation of apparatus 1 will now be described. Referring to FIG. 6, adapter means 38 is threaded onto base 46 of magnification means 42. Optical connector 32 is inserted into centering means 20 so that ferrule 30 protrudes above the surface of closed end 22.

[0043] Adapter means 38 is slipped over centering means 20 until it bottoms out against the surface of polishing workholder 34. Upon contact between adapter means 38 and polishing workholder 34, the axis of ferrule 30 is aligned with optical train axis 52. Additionally, the front surface of ferrule 30 is aligned with focal plane 50 of objective 44. This alignment permits the front surface of ferrule 30 to be viewed by optical magnification means 42.

[0044] In another embodiment of the present invention, apparatus 2 of FIG. 7 is shown with polishing workholder 34 formed with a plurality of grooves 54 on its front surface. Centering means 20 are located in the center of grooves 54.

[0045] Referring now to FIG. 8 an adapter means 38A and optical magnifications means 42 are illustrated. Adapter means 38A is tubular in shape and its cross sectional dimensions match that of groove 54. Suitable materials for adapter means 38A are stainless steel, aluminum, brass and polymer plastics. Stainless steel is preferred. One end of adapter means 38A has internal threading 40A that permits engagement with base 46 of magnification means 42. Adapter means 38A is of sufficient length, that when attached to base 46, the focal plane 50 of objective 44 lies within adapter means 38A. When attached to base 46, the center axis of adapter 38A coincides with the optical train axis 52 of magnification means 42.

[0046] The operation of apparatus 2 will now be described. Referring to FIG. 9, adapter means 38A is threaded onto base 46 of magnifications means 42. Optical connector 32 is inserted into centering means 20 so that ferrule 30 protrudes above the surface of closed end 22.

[0047] Adapter means 38A is pressed into groove 54 until it bottoms out. Upon contact between adapter means 38A and polishing workholder 34, the axis of ferrule 30 is aligned with optical train axis 52. Additionally, the front surface of ferrule 30 is aligned with the focal plane 50 of objective 44. This alignment permits the front surface of ferrule 30 to be viewed by optical magnification means 42.

[0048] In still another embodiment of the present invention, apparatus 3 of FIG. 10 illustrates an optical connector 32 mounted in a polishing workholder 34B. A ferrule 30 of optical connector 32 protrudes above the bottom surface of workholder 34B. Ferrule 30 has a center axis 60. Workholder 34B has a locating means 58 consisting of the workholder surface area that is surrounding protruding ferrule 30.

[0049]FIG. 11 illustrates an adapter means 38B attached to an optical magnification system 42. Adapter means 38B is tubular in shape and open at both ends. Suitable materials for adapter means 38B are stainless steel, aluminum, brass and polymer plastics. Stainless steel is preferred. One end of adapter means 38B has an internal threading 40B that permits attachment to a base 46 of optical magnification system 42. Adapter means 38B is of sufficient length that when attached to base 46, the focal plane 50 of objective 44 lies within adapter means 38B. Optical magnification system 42 has an optical train axis 52. The other end of adapter means 38B has an inner perimeter larger than the outer perimeter of a ferrule 30.

[0050] The operation of apparatus 3 will now be described. Referring to FIG. 12, adapter means 38B is threaded onto base 46 of optical magnification system 42. Optical connector 32 is inserted into polishing workholder 34B until ferrule 30 protrudes above the bottom surface of workholder 34B.

[0051] The other end of adapter means 38B is placed over ferrule 30 until it bottoms out against locating means 58. Upon engagement between adapter means 38B and locating means 58, the front surface of ferrule 30 is aligned with the focal plane 50 of objective 44. Adapter means 38B is then laterally moved about locating means 58 to align the center axis 60 of ferrule 30 with the optical train axis 52 of optical magnification system 42. 

We claim:
 1. An apparatus enabling the viewing of an optical fiber connector residing in a polishing workholder with an optical magnification system comprising: a centering means; an adapter means.
 2. The apparatus of claim 1 wherein said centering means is mounted in said polishing workholder.
 3. The apparatus of claim 1 wherein a ferrule of said optical fiber connector is positioned in the center of said centering means.
 4. The apparatus of claim 3 wherein the longitudinal axis said ferrule coincides with the longitudinal axis of said centering means.
 5. The apparatus of claim 1 wherein said adapter means is mounted on said optical magnification system.
 6. The apparatus of claim 1 wherein said centering means has a gender surface profile that is the anti-gender of the surface profile of said adapter means.
 7. The apparatus of claim 6 wherein the said gender surface and said anti-gender surface permit an engagement between said centering means and said adapter means.
 8. The apparatus of claim 7 wherein said engagement results in the longitudinal co-alignment of the said axis of said ferrule with the optical train axis of said magnification system.
 9. The apparatus of claim 7 wherein said engagement positions the end face of said ferrule at the focal plane of said optical magnification system.
 10. An apparatus which creates an engagement between a polishing workholder and an optical magnification device that locates the end face of a fiber optic component residing in said polishing fixture for inspection comprising: a locating means; an interface means.
 11. The apparatus of claim 10 wherein said locating means is a modified surface contour of said polishing workholder.
 12. The apparatus of claim 10 wherein said interface means attaches to the objective end of said optical magnification device.
 13. The apparatus of claim 12 wherein the front end of said interface means has a surface profile that allows it to mate with said locating means.
 14. The apparatus of claim 13 wherein said mating positions the end face of said fiber optic component along the optical train axis of said magnification device.
 15. The apparatus of claim 13 wherein said mating positions the end face of said fiber optic component in the focal plane of said magnification device.
 16. An apparatus which positions a ferrule of an optical fiber connector, protruding from a polishing workholder, into the focal region of an optical magnification system comprising: a locating means; an adapter means.
 17. The apparatus of claim 16 wherein said locating means is the bottom surface area of said polishing workholder surrounding said ferrule.
 18. The apparatus of claim 17 wherein said locating means is a positive stop for said adapter means upon engagement.
 19. The apparatus of claim 16 wherein one end of said adapter means attaches to said magnification system and the other end is formed to engulf the outer perimeter of said protruding ferrule upon engagement with said locating means.
 20. The apparatus of claim 16 wherein engagement between said locating means and said adapter means causes said ferrule of said fiber connector to lie in the focal plane of said magnification system. 